1. Field of the Invention
The invention relates to the field of telecommunications. In particular, the invention relates to telecommunications systems with connection processing systems.
2. Description of the Related Art
Asynchronous Transfer Mode (ATM) technology has become a well known means of communication. ATM is based on the 53 byte cell that contains a five byte header and a 48 byte payload. The header includes a virtual connection identification field known as the Virtual Path Identifier/Virtual Channel Identifier (VPI/VCI). The VPI/VCI is typically a 28 bit field that designates the virtual connection for the cell. The VPI/VCI is used by the network to route and handle ATM cells. Typically the VPI/VCI is used to identify a virtual connection, but other virtual channel identifiers could also be used in the context of the invention.
At present, VPI/VCIs are processed by using the VPI/VCI to access a memory location that stores processing instructions for the VPI/VCI. Using a 28 bit VPI/VCI to access memory is a cumbersome process. This entails writing the 28 bit VPI/VCI to one register and then repeatedly reading and writing successive VPI/VCI table entries into another register for comparison. This can entail several read/write operations before a match is found. The entire table must be searched if no match is available. This problem is compounded by processing over an 8 bit or 16 bit bus. With an 8 bit bus, a 28 bit number requires 4 write operations to transfer the number. A 16 bit bus requires 2 write operations. These conditions cause problems in broadband systems where high speed transport is used. VPI/VCI processing speed is often a critical factor. For example, when OC-3 transport is used to carry the ATM cells, a cell arrives for processing every 2.73 microseconds.
One solution is to restrict the number of bits that are actually used in the VPI/VCI. By restricting the 28 bit VPI/VCI to only 8 active bits, processing speed is improved. However, this limitation places severe restrictions on a network's ability to utilize the full capability of ATM virtual connection identification. As a result, this solution is often unacceptable.